Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy. The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. Hydropower is used primarily to generate electricity and broad categories are as follows: 1) A conventional dammed-hydro facility (hydroelectric dam) is the most common type of hydroelectric power generation 2) Run-of-the-river hydroelectricity, which captures the kinetic energy in rivers or streams, without the use of dams. 3) Small hydro projects are 10 megawatts or less and often have no artificial reservoirs. 4) Micro hydro projects provide a few kilowatts to a few hundred kilowatts to isolated homes, villages, or small industries. 5) Pumped-storage hydroelectricity stores water pumped during periods of low demand to be released for generation when demand is high. The greatest benefit from the use of hydropower is that it produces no carbon dioxide emissions or other harmful discharges, such as sulfur dioxide, carbon monoxide, and nitric acid, unlike the use of fossil fuels. Hydropower also generates no waste by-products and has no affect on today’s growing concerns with global warming Advantages of hydropower It is a clean and safe source of energy They are self sustaining They create habitat for more types of fish They can act as a flood controller.